Tensometer for simultaneously evaluating polymerization stresses, shrinkage and modulus development

Abstract

The present invention relates to apparatus and method for evaluating the development of PS during polymerization of dental restorative composites, which includes using a tensometer for measuring deflection of a calibrated cantilever beam induced by PS and calculating PS from the measured deflection. A tensometer according to an embodiment of the present invention can be used to quantify PS at varying beam locations and heights, and determine trend in PS development as a function of beam length. More importantly, in the present invention, the development of polymerization shrinkage and the elastic modulus can be simultaneously obtained in real time.

Description

STATEMENT OF FEDERAL RIGHTS[0001]This work was funded in part by the National Institute of Standards and Technology under the Department of Commerce.FIELD OF THE INVENTION[0002]The present invention generally relates to measurement of stress during curing of a polymer material and, more particularly, is concerned with evaluating the development of polymerization shrinkage and modulus during curing of a polymer material.BACKGROUND OF THE INVENTION[0003]Human tooth structures (mineral and proteinaceous components) are adversely affected by caries, and the resulting cavities usually do not fully regenerate. In such scenarios, the affected tooth frequently requires reconstruction using adhesive and restorative dental materials. Polymeric dental composites have been widely used in the restoration of tooth decay or cavity that occurs by primary caries or traumatic events. These materials, along with appropriate adhesives, are noted for their efficacy in restoring the function and appearan...

AI Technical Summary

Benefits of technology

[0007]Beam deflection measured by a tensometer according to an embodiment of the present invention reflects exclusively the specimen deformation due to shrinkage, and does not include deformation from the shrinkage-transmitting rods in the system. A tensometer according to an embodiment of the present invention takes into account geometrical conditions of beam. Further, periodic calibration of a tensometer according to an embodiment of the present invention can be performed without undue burden.

Problems solved by technology

Human tooth structures (mineral and proteinaceous components) are adversely affected by caries, and the resulting cavities usually do not fully regenerate.

However, these dental restorations may fail due to secondary caries, and replacement of failed restorations creates extra pain, anxiety, and economic burdens for the patients.

Dental restorations fail for a variety of reasons.

For example, magnified stresses (stress singularity) at or near the tooth / composite interface due to the mismatch of tooth and restorative mechanical properties are important contributors to failure.

This shrinkage can lead to marginal micro cracks and subsequent micro leakage at or near the composite-tooth interface, which permits bacteria to pass beneath the restoration surface and ultimately cause secondary (recurrent) caries.

Further, calibration of the existing system needs compressed air and a load cell (extra instrumental setups) and unnecessary experimental procedures, which become a burden for periodic recalibration of the system.

Furthermore, the existing system is solely used for the measurement of polymerization stress development, which cannot be functionally related to the extent of polymerization shrinkage or the modulus development.

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